Ballast for gaseous discharge devices



Dec. 27, 1949 MAUERER 2,492,389

BALLAST FOR GASEOUS DISCHARGE DEVICES Filed Aug. 27, 1948 2 Sheets-Sheet 1 Dec. 27, 1949 Filed Aug. 27, 1948 L- MAUERER BALLAST FOR GASEOUS DISCHARGE DEVICES 2 Sheets-Sheet 2 jeo void Patented Dec. 27, 1949 Leopolddvlauerer, Chicago, 111;; assign'or toJelfers soniElectricOompany; Bellwoodfllli, a corpora) tion of Illinois Application August 27, 1948, Serial No. 461407 7 Claims. 1;:

This invention relates toan improvedballast for gaseous discharge devices;

The type of ball'ast to wh ich this invention is primarily directed isa=twos=lamp ballast having three separate windings arranged. on "a common core. The middle winding constitutes the primary and secondary:coils:of -atranSiQrmer; and the end windings constitute: reactors; one :reactor being provided 'for each of the gaseous discharge devices The transformer may-beeither-bf the insulated or of the autotran'sformer. type, and each of the-circuits;inoluding-oneof the reactors, and one of the gaseouscdischarge. tubes, are con.- nected in para1le1 withi=each other. acrossthe secondary of the transformer: In other words, the transformer providesrawsecondary'coil which is common to .bothi'of .th'eisecon'daryv circuits;

It is an'object: of:imyk inventionntoprovide. a ballast of thistype whichi is.characterized.by .low

manufacturing 1 costs; improved efficiency, Y and silence of operation. More" specifically; IjpI'O-r vide. a core structurewawhichz:iswformedxfrom two identical stampingmiboth ofiiwhich-are comparatively long. with::respect :to:.their width; Core laminationss'areistamped :from strip; stock 'which is advanced. toward ithe dien. Byvproviding-a lamination shape-.oicomparatively; small :width, the rate of stampingais considerably increased. since the step by. step: movement of the stripqis.v comparatively small.

Manufacturing cost is further; reduced: by: the fact that there .isverysmall. waste of stocl 1 in stamping outv the: laminations. Furthermore, since the core structure isbuilt up from only two stacks of laminations which areassembled merely by abutting. them :together; the assembly diificulties in certain priorart-bal-lasts which require three or more stacks' 'to be: maintained vinxalignment are obviated.

It has further been found. that there is greater reluctance and greatercorelosses when the flux runs across the-grain of. thelamination material than when it runs parallel to the. grain. A further object of this. invention is. to provide. a ballast in which the windingsand thecore are so arranged that'the major portion of 'theflux path of each winding 'is"disposedparal'lel' to "the grain of the lamination material, thereby reducing the reluctanceflan'dthe iron'losses.

A still further object. is to provide a ballast in which air aps are. provided in the winding legs of thereactor coils; and'in'whichtheair gap is completely 'surroundedby' the reactorcoil. Thus, an arrangement is produced which reduces the leakage fluxvvhich'goes through the casewith 2. the result that hum due to vibration of the-wall of-=the=-'-casing is substantially eliminated Iron losses inthe case are also reduced by'this arrangement;

Furthermore, inthe present arrangement, the width'of 3 the air gaps is determined bythedie which stamps-out the' laminations. Thus; more uniform electrical characteristics can be-obtained, than when each transformer is individually gapped on test.

Still "another obj ect is to provide a ballast in which thetransformer and reactor windings are arranged on para1le1-axes;=thereby permitting the use ofmoreeffi'cient coil proportions. One-type of fluorescent lamp fixture now incommon use calls for along and narrowballast. The usual prior art ballast of thistype-hasthe -coils arranged "coaxially, and this results in a long coil o f comparatively-small diameter and-in which the cross section of the coil and the window required thereby has a length to width ratio of as great as six to one. The-present:invention permits the use of coils having acoil cross section ratio of as little as three to one which reduces the intra coil leakage-=toa minimum ascontrasted with the longer and 'na'rrower coils of the prior art ballasts.

A' stillfurther-cbjectis to providea ballast which is less subject to over-heating. Dueto the fact that the core is -formedfrom only two stacks, each of'whi'ch partially lin'kthree separateWind-- ings, there'is1ess danger of localized over-heating due-to ahea-vy current carried by one coil. This is for *the reasonthat the core will serve: to corrduct-"theheat away irom one coiland-*distribute it uniformlythroughout'the-whole core,- which is not-the case-when aseparate core stack is used for each win-ding.

Other-objects, features and advantageswill be+ comeapparent "as the description proceeds.-

With-reference now to 'thedrawings in. which 1ike-reference numerals designated. like parts:

Fig; l'is a top viewof a ballast madeinaccordance within'y invention; the casing :being removed;

Fig: 2 isan elevatiorrof *theballastof Fig. 1, and also showing the casing in"section;'

Fig. 3 isa-secti'on-taken along liner3 -3 of Fig. 2 and'whichalso shows the casing -in section;

Fig; 4 is an elevation of a single "lamination;

Fig: 5is- -a* diagrammatic representation of a lighting system'embodyingmy invention, and

Fig-:6 is a-section taken-alongline 6 -6 "of Fig. 3.

The ballast is designated generallybythe-reference numeral Hland' includesa casing H and-a core I [which is disposed within the-casing. The core hasa middle-winding leg 3 and two outer winding legs I4, I which are parallel to the middle winding leg. A transformer winding 16 is disposed on the middle winding leg. The transformer winding may be of the insulated type or of the autotransformer type. As shown in Fig. 5 the transformer winding comprises a secondary coil l1 and a primary coil [8 which are connected together in autotransforiner relationship.

On the outer winding legs It and I5 are mounted reactor windings 20 and 2! respectively, these being connected in series with the secondary coil l l as shown in Fig. 5. A condenser I9 is connected in series with reactor winding 2|, and a gaseous discharge tube 25 is connected in series with the reactor 2| and condenser ill by means of conductor 23. Similarly, a conductor 22 connects the tube 24 in series with reactor 20. A common conductor 26 connects the opposite ends of the tubes 24 and 25 to the primary coil I8. Primary leads 2? and '28 supply power to the primary.

As shown in Figs. 1 and 3, the core l2 comprises two lamination stacks and 3|, each of which are formed from a plurality of identical laminations 32, one of which is shown in Fig. 4. The lamination is an elongate member stamped from suitable steel stock in which the direction of the grain runs across the shorter dimension, as shown by the arrow 33. Lamination material comes in long strips, the grain direction of which runs the length of the strips. Thus, in stamping the laminations 32, stock is advanced with respect to the die at each stamping operation, only by a distance which substantially equals the width of the lamination strip 32. Thus, stamping may be effected at much more rapid rate than in the case of other types of laminations which are now on the market.

One of the longitudinal edges of the lamination strips may be considered as the abutting edge 34, since this is the edge which abuts the corresponding edge of an oppositely disposed strip. Three pairs of slots extend inwardly from the abutting edge 34. Slots 35 and 3&3 define a tongue portion Ha which constitutes one-half of the winding leg 14. Slots 3'! and 38 define a tongue portion l3a which constitutes a portion of the winding leg l3. Slots 39 and dc define a tongue portion 15a which constitutes a portion of the winding leg I511. The remaining tongue portions are indicated by the reference numerals i i-M inclusive and constitute yoke portions, since they provide return paths for the flux which is produced by the various coils which are positioned on the winding legs.

The tongue portions I la and i511 are somewhat shorter than the remaining tongue portions so that when two laminations are arranged in the intended abutting relationship, air gaps 4'6 and 41 will be provided in the outer winding legs l4 and I5 respectively. Since the width of this gap is determined by the lengths of the tongues Ma and Mia, the width will be uniform, not only for all pairs of lamination in a given core but also for all cores in a given production run. Thus, uniform electrical characteristics are provided.

Since the gaps 46 and 41 are disposed within the coil, any fringing or stray flux which occurs due to the presence of the gap will not effect the transformer casing l I which is formed from magnetic material. Thus, casing hum is eliminated.

The air gaps 46 and 41 may be filled with gapping material if desired, but I have found that there is no appreciable hum even when the gaps are not filled. This is believed to be due to the fact that that portion of the length of each stack which is subject to flexing is comparatively small with respect to that portion which is subtended by abutting tongue portions, and hence not subject to flexing.

However, if gapping material is used, the present arrangement lends itself ideally to the use of a cement for the gapping material. For instance, an amount of cement can be placed on the edge surfaces of the outer winding legs 54 and 15 which amount is slightly in excess of that required. In the process of abutting the lamination stacks, the excess cement is squeezed laterally out of the gaps 46 and 4'! with the result that the gap is completely filled. Since the gap is surrounded on all sides by the coil spool, the cement which is a semi-conductor when wet will not damage or affect any current carrying parts.

The laminations may be formed so as to provide the proper spacing between the three separate windings. As shown in the drawings, there is a greater spacing between the windings 26 and it than between the windings 2| and it.

As shown in Fig. 4, the corners of the lamination 32 are clipped off as indicated by the reference numeral 50, and notches 5! are formed opposite tongue portions Ma, 42, Mia and l5a. These notches provide a space for the compound (not shown) to work its way into the comparatively small space between the core and the casing. The stamping of these notches in the edge opposite the longitudinal abutting edge 3 1 is also believed to distribute any internal strain which results from the stamping of the slots 35 to ll) inclusive. Thus, any tendency of the lamination to warp or bend is overcome.

The lamination stacks 30 and 3| may be secured to each other by any suitable clamping means. As shown in the figures, I prefer to use clips 52 which serve to connect the abutting tongue portions ll-44 inclusive. These clips are of the type disclosed in my Patent No. 2,378,233, issued June 12, 1945. As shown in Fig. l, the clips are secured to the lamination stack 31 by means of rivets 53, and a tongue portion 54 of each clip 52 engages a headed pin 55 which passes through lamination stack 32. When the tongue portions are brought into final position the two lamination stacks will be drawn into tightly abutting relationship.

During operating conditions, that is, when the tubes 24 and 25 are illuminated, the current in the tube circuit 25 will be leading and the current in the tube circuit 24 will be lagging. The values of the condenser i9 and reactor winding 2| are such that there is a preponderance of capacitive reactance during operating conditions, and this preponderance of capacitive reactance substantially offsets the inductive reactance provided by the reactor winding 20. Thus, the power factor of the supply current is substantially unity during normal operating conditions. This is standard practice, and by the term power factor of substantially unity is meant anything between and either leading or lagging, since the standard practice varies within these limits.

Under open circuit conditions, when no current is flowing, there will be substantially no voltage drop across the reactors 20 and 2| and across the condenser [9 with the result that the full voltage of the transformer winding It will be applied across the tubes. As soon as the tube ignites, however, the desired ballasting action is provided by the aforementioned elements with the result that the desired operating voltage is obtained.

The usual starting circuits are provided for the tubes 24 and 25, these circuits being indicated generally by the reference numerals 56 and 57 respectively. The starting circuit 56 for the lag tube includes starter 58, and the circuit for the lead tube includes starter 59 and a compensating coil 65. The coil 60 may be incorporated with the reactor winding 2| With the result that it does not appear as a separate coil in Figs. 1 to 3 inclusive.

If desired, the ballast herein shown and described may be used in two-lamp circuits other than that shown in Fig. 5. For instance, an additional condenser may be provided so that both tube circuits are leading.

Irrespective of the particular type of circuit, I have found that the core arrangement of my invention provides a ballast of improved and uniform electrical characteristics as well as a ballast that is easy to assemble, and that costs less to manufacture.

For instance, the parallel disposition of the windings permits the use of more eflicient coil proportions. Furthermore, the heat developed in one portion of a lamination stack under heavy load conditions will be immediately conducted to other portions of that stack which are remote from the particular winding which is affected by the heavy current drawn. Thus localized overheating is eliminated.

I claim:

1. A ballast for two fluorescent lamps comprising a core having a middle winding leg, two outer winding legs the axes of which are spaced from the axis of said middle winding leg and are disposed parallel thereto, and four yoke portions the axes of which are parallel to the axes of said winding legs, two of which yoke portions are disposed between adjacent winding legs, and two of which are disposed exteriorly of said outer winding legs, a transformer winding disposed on said middle winding leg, two reactor windings, each being disposed on one of said outer winding legs, and a casing of magnetic material enclosing said core and said windings.

2. A ballast as claimed in claim 1 in which said core is formed from two abutting lamination stacks formed from identical laminations.

3. A ballast as claimed in claim 2 in which each lamination comprises an elongate strip having a longitudinal abutting edge, and in which the grain of the stock from which the lamination is formed runs perpendicular to said longitudinal abutting edge.

4. A ballast for two fluorescent lamps comprising a core having a middle winding leg, two outer winding legs spaced from and disposed parallel thereto, and four yoke portions, two of which are disposed exteriorly of said outer winding legs and two of which are disposed between adjacent winding legs, a transformer winding disposed on said middle winding leg, two reactor windings, each being disposed on one of said outer winding legs, and a casing of magnetic material enclosing said core and said windings, said core being formed from two abutting lamination stacks, the laminations in both stacks being identical to each other, and each lamination comprising an elongate strip having a longitudinal abutting edge provided with a plurality of slots therein to provide a plurality of parallel tongue portions which form said winding legs and said yoke portions.

5. A ballast as defined in claim 4 in which the end tongue portions are at least as long as any of the other tongue portions in order to provide a closed magnetic path at points adjacent said casing to prevent establishment of a fringing flux which affects said casing when a pair of like laminations are abutted.

6. A ballast as claimed in claim 5 in which the tongue portions adjacent to said end tongue portions are shorter than said end tongue portions in order to provide air gaps in said outer winding legs when a pair of like laminations are abutted.

7. A ballast for two fluorescent lamps comprising a core having a middle winding leg, two outer winding legs disposed parallel thereto, four yoke portions, two of which are disposed between adjacent winding legs, and two of which are disposed exteriorly of said outer winding legs, a transformer winding disposed on said middle winding leg, two reactor windings, each being disposed on one of said outer winding legs, and a casing of magnetic material enclosing said core and said windings, said core being formed from two abutting lamination stacks, the laminations in both stacks being identical to each other, and each lamination comprising an elongate strip having a longitudinal abutting edge provided with six slots therein to provide seven tongue portions, the second and sixth tongue portions constituting portions of said outer winding legs and being shorter than the remaining tongue portions in order to provide air gaps when a pair of like laminations are abutted, and the first and seventh tongues being at least as long as any oi said remaining tongue portions to avoid presence of an air gap adjacent said casing in order to prevent establishing of a fringing flux which affects said casing when a pair of like laminations are abutted.

LEOPOLD MAUERER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,425,622 Kronmiller Aug. 12, 1947 2,441,213 Sutter May 11, 1948 

